1. Field of the Invention
The present invention is a recovery system. More specifically, the present invention is an ammonia capture recovery system.
2. Description of the Related Art
Wastewater streams rich in the nutrients nitrogen and phosphorus are produced by municipal, industrial, and agricultural processes. These nutrients are present in various forms: partially bound to solids and not immediately available to the ambient air and water, and in water soluble forms (phosphate, nitrate, ammonia, organic nitrogen), and in the case of ammonia in a volatile gas form.
All three categories are present in anaerobic digestion effluent known as digestate. The soluble and volatile forms of these elements are particularly prone to loss pathways and pose a variety of environmental and human health threats.
Ammonia that is captured and fixed chemically may be utilized in agriculture as fertilizer or industrially as a process chemical. The liquid product of digestion of organic waste, or digestate frequently contains relatively high concentrations of dissolved ammonia in the form of ammonia gas and ammonium ion. Nitrogen in these forms, ammonia or ammonium, is termed NH3—N. Ammonia from a liquid digestate may be readily diffused from the liquid digestate and converted to a chemical fertilizer which provides a uniform, high purity, concentrated source of NH3—N. As with synthetic fertilizer, the material is nearly odorless and has low transport and application costs relative to manure and the liquid digestate.
Ammonia stripping from wastewater through the utilization of hot air and steam is well established. These methods generally employ industrial acid to capture the stripped ammonia, where normally sulfuric acid is utilized. The utilization of acids is highly effective in both ammonia recovery and in producing a concentrated ammonium salt product. However the stripping methods involve utilization of relatively large and expensive vessels and substantial inputs of thermal and electrical energy to liberate the ammonia. It would be advantageous to utilize a combination of filtration methods to separate the digestate ammonium from particulate and colloidal solids and organic solutes and efficient utilization of hydrophobic membranes to capture the ammonia as technical grade ammonium salt to greatly reduce these negative attributes of conventional ammonia stripping.